Drive unit for a fan and arrangement with  a drive unit

ABSTRACT

The invention relates to a drive unit for a fan of an internal combustion engine of a vehicle, having a friction clutch which can be shifted in order to drive the fan via the internal combustion engine. An electric motor is also provided for driving the fan, and a torque-transmission path is formed between the friction clutch and the fan by means of a rotatably mounted part of the electric motor. The invention also relates to an arrangement for driving a fan via an internal combustion engine with a drive unit that includes an electric motor and a friction clutch.

This application claims the benefit under 35 USC §119(a)-(d) of GermanApplication Nos. 10 2008 058 377.4 filed Nov. 20, 2008 and 10 2009 011347.9 filed Mar. 5, 2009, the entireties of which are incorporatedherein by reference.

FIELD OF THE INVENTION

The invention relates to a drive unit for a fan and an arrangement witha drive unit.

BACKGROUND OF THE INVENTION

Fan systems or cooling systems and arrangements with such systems areknown in vehicles, in particular in motor vehicles with internalcombustion engines. In contemporary systems, in particular, multi-stageelectromagnetic clutches or what are referred to as viscous clutches areinstalled. In such cases, a considerable loss of power may occur in alow rotational speed range of a fan of the cooling system via a systemwhich is continuously subject to slip. Viscous clutches can ensure, inparticular, free setting of the rotational speed of the fan drive aslong as a power loss does not exceed certain operating limits. In thiscontext, power losses of several kilowatts which depend on theparameters of the fan torque and differential rotational speed of thecoupled rotating elements can be produced. Disadvantages are found tooccur with viscous clutches in particular in a cold start phase or inthe case of deactivation.

If multi-stage electromagnetic clutches are used for operating a fan,said fan can be deactivated completely. There is no permanent slip inthe switched-on state. However, control can be carried out only to alimited degree with electromagnetic clutches.

SUMMARY OF THE INVENTION

The object of the present invention is to make available a drive of acooling system for a vehicle having an internal combustion engine, whichdrive can advantageously be adapted to the operating states which arerelevant in practice, in particular while avoiding the disadvantageswhich have occurred hitherto with drive systems of the generic type.

The invention is based firstly on a drive unit for a fan of an internalcombustion engine of a vehicle, having a friction clutch which can beshifted in order to drive the fan via the internal combustion engine.The core of the drive unit according to the invention is that anelectric motor is also provided for driving the fan, and that atorque-transmission path is formed between the friction clutch and thefan by means of a rotatably mounted part of the electric motor. Theelectric motor has, in particular, a stator and a rotor which can rotatein relation to one another.

The invention permits a drive unit to be obtained which is advantageousin terms of improved control and comfortable adaptation of the fan powerin the low power range by means of a desired or settable fan rotationalspeed. In addition, relatively high or maximum fan power levels can beimplemented for selected operating states, for example.

The drive unit according to the invention combines, in particular, theadvantages of a viscous clutch and the advantages of a multi-stagefriction clutch, for example of an electromagnetically actuablefrictionally engaging clutch. With the proposed drive unit it ispossible to implement a free rotational speed setting as long as thepower loss does not exceed its operating limits. Furthermore, the driveeffect on the impeller wheel can be completely deactivated or switchedon without permanent slip. A direct drive by a drive shaft to theimpeller wheel or an impeller wheel hub is possible 1:1. Overall, thedrive according to the invention is advantageous, in particular, forutility vehicles.

In particular, in the case of hybrid vehicles which generally have, forexample, an on-board electrical voltage range to above 400 volts, anelectric motor with an electrical power level of approximately 5 kW canbe made available without problems. With the electric motor which can beswitched on and off it is possible to implement a first operating stateaccording to which the impeller wheel is not driven, and also a secondoperating state with control as far as approximately 5 kW.

In practice, power peaks which occur cannot, however, be appropriatelycovered in terms of the radiator power or fan power with an electricmotor which can reasonably be used in the vehicle, since the sizes ofelectric motor which are necessary for this purpose are uneconomical orthe installation situation is impractical due to complex cabling.

Power peaks can therefore be covered according to the invention by meansof a simple friction clutch, in particular, for example, anelectromagnetic clutch.

The invention therefore allows, in particular, for the fact that, forexample, for utility vehicles, in practice cooling of the cooling systemgenerally occurs as a result of the relative wind for 80% of the time ofuse. The fan power of a maximum of approximately 5 kW is required forapproximately 18% of the operating time. Only in 2% of the operatingtime is a relatively high to maximum fan power level required. Theseoperating states can be advantageously covered with the drive unitaccording to the invention. It is also advantageous that, even when theinternal combustion engine is stationary, a cooling power level of amaximum of 5 kW is possible by means of the electric motor.

It is also advantageous that the friction clutch is designed to permitdirect drive of the fan by the internal combustion engine.

The friction clutch can advantageously be embodied as anelectromagnetically actuable friction face clutch, for example, as afriction disk clutch. A slip-free connection of a motor-side drive shaftand of a fan-side fan shaft can therefore be made possible in anon-positively or frictionally locking fashion.

Furthermore, it is advantageous that a rotationally flexible clutch isprovided for driving the fan by the internal combustion engine. The fancan be driven, for example, at a rotational speed which is relativelylow with respect to the rotational speed of the internal combustionengine by means of the rotationally flexible clutch. It is thusbasically possible to provide a drive of the impeller wheel which issubject to slip in addition to or instead of the direct drive. Atorque-dependent overload protection can be implemented by means of therotationally flexible clutch, and this can be advantageous in certainapplications. For example, an eddy current clutch is possible as arotationally flexible clutch.

In addition, it is possible that, in the installed state, the frictionclutch and the electric motor do not extend, or only extendinsignificantly, over a diameter of an impeller wheel hub of the fan ina radial direction. It is therefore possible to implement a particularlycompact design of the drive unit. In particular, installation spacewhich is necessary in any case in the radial direction, in particularwith respect to an axis about which the fan or an impeller wheel canrotate during operation, can be used, which easily permits integrationor retrofitting of the drive unit according to the invention forexisting assemblies.

It is also advantageous that the electric motor has a housing to whichthe fan is attached. It is therefore possible to implement aparticularly stable and space-saving arrangement. In particular, nointermediate connecting parts are necessary between the electric motorand the fan. The fan itself can also be embodied as in previous systems.

In one particularly advantageous modification of the subject matter ofthe invention, the friction clutch and the electric motor are combinedto form one structural unit. This facilitates the installation ordisinstallation of the drive unit. Furthermore, the entire drive withthe drive unit can therefore be configured in a compact fashion.Furthermore, the parts of the friction clutch and of the electric motorcan, if appropriate, be accommodated in a protected fashion in a commonhousing.

The friction clutch and the electric motor are advantageously connectedto form one unit, which is advantageous in terms of optimum utilizationof space.

The invention also relates to an arrangement for cooling an internalcombustion engine having a radiator for cooling the internal combustionengine, and a fan which interacts with the radiator, wherein a driveunit for the fan is present in accordance with the details explainedabove. The cooling arrangement for the internal combustion engine cantherefore be embodied in accordance with the advantages specified above.

The drive unit preferably comprises a friction clutch and an electricmotor which are combined to form one structural unit, wherein thestructural unit is connected to the radiator. The fan generates an aircurrent which is conducted past faces of the radiator in order toeffectively bring about a transmission of heat from areas of theradiator to the air flowing around.

Moreover, it is advantageous that the drive unit comprises a frictionclutch and an electric motor which are embodied separately. This permitsadvantageous installation, disinstallation and utilization of anexisting installation space.

Furthermore, it is possible that the friction clutch can be arranged onthe internal combustion engine. This can be advantageous depending onthe application or prevailing installation conditions.

Finally, it is also advantageous that the electric motor is attached tothe radiator, in particular the entire drive unit composed of the clutchand electric motor. This may be advantageous in terms of a compactdesign of the drive unit or for reasons of installation.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and features of the invention will be explained inmore detail with reference to three exemplary embodiments of theinvention which are illustrated in a highly schematic form.

FIG. 1 shows a schematic view of a drive unit according to the inventionwhich is attached on the radiator side;

FIG. 2 shows an alternative drive unit according to the invention whichis arranged on the motor side; and

FIG. 3 shows a third inventive embodiment variant of a drive unit, withan electric motor being arranged on the radiator and a friction clutchbeing arranged on the motor.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a highly schematic view—which omits components—of a drive unit1 according to the invention in the installed state, for example, in avehicle with an internal combustion engine 3, for example a dieselengine, with the internal combustion engine 3 being only shown in blockform. The drive unit 1 is to be understood as being the part of thedrive for an impeller wheel 2, and in this context the drive unit 1 doesnot include the internal combustion engine 3 itself.

The drive shaft 4 is connected to the drive unit 1 via a flange 4 a of adrive shaft 4 (shown only partially) of the internal combustion engine3.

The impeller wheel 2 (illustrated only partially or in a hub region) isaccommodated on a central impeller wheel hub 2 a which is connected in arotationally fixed fashion to a fan shaft 5 via which the impeller wheel2 can be driven in rotation. The fan shaft 5 is embodied over its mainlongitudinal extent as part of an electric motor 6 and forms a rotor 8of the electric motor 6. The rotor 8 is surrounded by a stator 7 of theelectric motor 6. The stator 7 is attached in a positionally fixedfashion to a radiator section 9 and to a vehicle frame (not illustrated)via the radiator section 9. The stator 7 is supported with respect tothe rotating rotor 8 by means of bearings 10 and 11, for example rollerbearings.

A friction clutch 12 is provided between a drive flange 17 connected ina rotationally fixed fashion to the flange 4 a, and the electric motor6, on that side of said electric motor 6 which faces toward the internalcombustion engine 3. The friction clutch 12 is embodied as anelectromagnetically actuable friction disk clutch. For this purpose, anelectromagnet arrangement 13 with a positionally fixed electromagnet 14is provided, the electromagnet 14 generating magnetic forces as a resultof energization of the electromagnet arrangement 13, as a result ofwhich an armature disk 15, which can be moved axially with respect tothe fan shaft 5 in a resettable fashion, is attracted to a friction ringsection 16 that is rotationally fixed to fan shaft 5. In this way, it ispossible to establish a coupling connection for a maximum cooling powerin the case of power peaks of the radiator, and as a result also of thefan 2 with a direct transmission of rotational speed taking place fromthe drive shaft 4 to the fan shaft 5, and therefore to the fan 2, viathe drive flange 17 and the friction ring section 16.

The drive flange 17 is rotatably mounted on the fan shaft 5 by means ofa bearing 18, at the axial end of the fan shaft 5 which is directedtoward the internal combustion engine 3. When the electromagnetarrangement 13 is not energized, the armature disk 15 is separated fromthe friction ring section 16 by resettable spring means, for example bymeans of a spring ring 19, as a result of which no drive connection isproduced between the drive shaft 4 and the fan shaft 5.

However, in this state, the drive unit 1 can drive the fan via theelectric motor 6 if a comparatively low cooling power is required forthe radiator (not illustrated). The fan 2 can be operated in aninfinitely variable fashion, for example to approximately 5 kW power viathe controllable electric motor 6. Unless current is applied to theelectric motor 6 and the electromagnet arrangement 13, the impellerwheel remains stationary or does not experience any motor drive effect.

The drive unit 1 with the electric motor 6 and the friction clutch 12can advantageously extend in the radial direction with respect to therotational axis S of the fan shaft 5 over a region a which is almostcompletely in the diameter region of the impeller wheel hub 2 aaccording to FIG. 1. According to the exemplary embodiments in FIG. 2and FIG. 3, a drive unit according to the invention can also be locatedcompletely within the radial extent of an impeller wheel hub.

It is also advantageous that the drive unit 1 can, for example, befixedly arranged with the drive flange 17 on the radiator section 9.Vibrations or oscillations which occur during operation of the internalcombustion engine 3 are therefore not transmitted to the impeller wheel2. A circumferentially extending gap (not illustrated) which is presentradially on the outside of the impeller wheel 2, with respect to theadjoining sections, for example an air guiding ring on the radiator, cantherefore be selected to have the minimum size, if appropriate in themillimeter range. Disruptive air eddying formations at the radial outeredge of the impeller wheel 2 can therefore be advantageously avoided orminimized. If a drive unit were to be mounted on the internal combustionengine 3, a significantly larger size would have to be disadvantageouslyselected for this gap in order to prevent contact between the impellerwheel and air guiding ring means. This has a negative effect on theformation of flow by the impeller wheel.

An alternative arrangement according to the invention with a drive unit20 is shown in FIG. 2. Said arrangement likewise serves to drive animpeller wheel 21 on an impeller wheel hub 21 a. Furthermore, aninternal combustion engine 22 for driving the impeller wheel 21 ispresent. An electric motor 23 of the drive unit 20 for a drive operationof the impeller wheel 21 which can be controlled in an infinitelyvariable fashion is present spatially between the internal combustionengine 22 and the impeller wheel 21. The electric motor 23 comprises arotor 24 which is fixedly connected to the impeller wheel hub 21 a andwhich is mounted by means of bearings 21 and 26 with respect to a stator27 which is arranged in a positionally fixed fashion on the internalcombustion engine 22. The cylindrical stator 27 therefore has a gap withrespect to the impeller wheel hub 21 a on the fan-side end of saidstator 27.

Furthermore a friction clutch 28 is present between the internalcombustion engine 22 and the electric motor 23. The friction clutch 28comprises an electromagnet arrangement 29 with an electromagnet 30, bymeans of which, when the electromagnet 30 is energized, an axiallydisplaceable armature disk 31 can be connected to a section 33 a of abelt pulley 33 in a frictionally or non-positively locking fashion viaspring means, for example a spring ring 32, which can be displaced inthe axial direction with respect to the rotor 24. The belt pulley 33 isrotatably mounted on the stator 27 by means of a roller bearing 34 andcan be driven in rotation by the internal combustion engine 22 by meansof belts (not illustrated). For this purpose, a belt support section 33b is present on the outer circumference of the belt pulley 33.

When the electric motor 23 is operating, the impeller wheel hub 21 a andtherefore the impeller wheel 21, are made to rotate in a regulated,infinitely variable fashion, by rotating the rotor 24 with said electricmotor 23.

When the electric motor 23 and the electromagnet arrangement 29 are notenergized, the impeller wheel 21 is not driven in rotation. If only theelectromagnet arrangement 29 is energized when the electric motor 23 isnot being operated, the rotor 24 which runs on the outside and thereforealso the impeller wheel 21, are driven directly via the shifted frictionclutch 28 via the belt pulley 33 and the engaged friction clutch 28.

In the arrangement of the inventive drive unit 20 shown in FIG. 2, theelectric motor 23 and the friction clutch 28 are embodied as astructural unit which is positioned between the impeller wheel 21 andthe internal combustion engine 22.

A further arrangement of an inventive drive unit 34 is shown in FIG. 3.According to this embodiment, the drive unit 34 is divided into twounits. A first unit is formed by the electric motor 35, which is heldfixedly connected by its stator 36 to a radiator section 38. The stator36 is mounted, by means of bearings 39 and 40 on the rotor 37 whichrotates together with an impeller wheel hub 41 a. An impeller wheel 41is secured to the impeller wheel hub 41 a. The rotor 37 forms part of animpeller wheel shaft 42. The impeller wheel shaft 42, which isillustrated in an interrupted fashion in FIG. 3, can be connected in arotationally fixed fashion to a drive shaft (not shown) of an internalcombustion engine 43 via a friction clutch 44, and can be disconnectedfrom a drive effect of a drive shaft by means of the friction clutch 44.The friction clutch 44 is only illustrated in a highly schematic fashionor in a box form. The friction clutch 44 can be embodied, in particular,in the form of an electromagnetic clutch which can be shifted.

LIST OF REFERENCE NUMERALS

-   1 Drive unit-   2 Impeller wheel-   2 a Impeller wheel hub-   3 Internal combustion engine-   4 Drive shaft-   4 a Flange-   5 Fan shaft-   6 Electric motor-   7 Stator-   8 Rotor-   9 Radiator section-   10 Bearing-   11 Bearing-   12 Friction clutch-   13 Electromagnet arrangement-   14 Electromagnet-   15 Armature disk-   16 Friction ring section-   17 Drive flange-   18 Bearing-   19 Spring ring-   20 Drive unit-   21 Impeller wheel-   22 Internal combustion engine-   23 Electric motor-   24 Rotor-   25 Bearing-   26 Bearing-   27 Stator-   28 Friction clutch-   29 Electromagnet arrangement-   30 Electromagnet-   31 Armature disk-   32 Spring ring-   33 Belt pulley-   33 a Section-   33 b Belt support section-   34 Drive unit-   35 Electric motor-   36 Stator-   37 Rotor-   38 Radiator section-   39 Bearing-   40 Bearing-   41 Impeller wheel-   41 a Impeller wheel hub-   42 Impeller wheel shaft-   43 Internal combustion engine-   44 Friction clutch

1. A drive unit for a fan of an internal combustion engine of a vehicle,comprising a friction clutch that is shifted in order to drive the fanvia the internal combustion engine, and an electric motor for drivingthe fan wherein a torque-transmission path is formed between thefriction clutch and the fan by a rotatably mounted part of the electricmotor.
 2. A drive unit according to claim 1, wherein the friction clutchpermits direct drive of the fan by the internal combustion engine.
 3. Adrive unit according to claim 1, wherein the friction clutch is anelectromagnetically actuable friction face clutch.
 4. A drive unitaccording to claim 1, further comprising a rotationally flexible clutchfor driving the fan by the internal combustion engine.
 5. A drive unitaccording to claim 1, wherein the friction clutch and the electric motordo not substantially extend in the radial direction beyond a diameter ofan impeller wheel hub of the fan.
 6. A drive unit according to claim 1,wherein the electric motor comprises a housing to which the fan isattached.
 7. A drive unit according to claim 1, wherein the frictionclutch and the electric motor are combined to form one structural unit.8. An arrangement for cooling an internal combustion engine, comprisinga radiator for cooling the internal combustion engine, a fan whichinteracts with the radiator, and a drive unit according to claim
 1. 9.An arrangement according to claim 8, wherein the drive unit comprises afriction clutch and an electric motor, that are combined to form onestructural unit that is connected to the radiator.
 10. An arrangementaccording to claim 8, wherein the drive unit comprises a friction clutchand an electric motor, which are embodied separately.
 11. An arrangementaccording to claim 8, wherein the friction clutch is arranged on theinternal combustion engine.
 12. An arrangement according to claim 8,wherein the electric motor is attached to the radiator.